Microfluidics, the technology of manipulating small fluid volumes, has been widely used for many applications in biomedicine, labs-on-a-chip (LOC) analysis, and cell biology, among others. Traditionally, microfluidic devices have been fabricated in solid materials such as silicon or glass using photolithography techniques. In some such conventional embodiments, the solid substrate materials may typically be substantially inflexible and/or exhibit very limited flexibility. While photolithography has enabled the development of microfluidic channels and devices in micro-scale, the use of photolithographic techniques to fabricate microfluidic devices has typically required at least one of expensive equipment, long fabrication time, and complex processes.
As flexible technologies have been introduced and developed for microfabrication, polymers such as polydimethylsiloxane (PDMS) have been commonly used, and PDMS in particular has been popular for such use due to its low toxicity, thermal stability, and low cost. Also, development of soft lithography techniques such as microcontact printing, replica molding, or microtransfer molding, which typically utilize polymers, has enabled fabrication of more flexible microfluidic channels and devices in micro-scale. However, such polymer based microfluidic channels and devices have been typically bonded to silicon or glass substrates in systems using such soft lithographic techniques. Although PDMS itself is mechanically flexible, the use of rigid substrates has hindered development of fully flexible microfluidic devices that can conform to curved surfaces.
In addition to flexible technology, more specifically wearable technology has become of significant interest in recent years. The use of microfluidic sensors and monitoring systems on clothes or other wearable items are desired for their potential to improve human life. For example, wearable motion sensors may be desirable for use in rehabilitation, and wearable biosensors may be desirable for use in real-time bio-signal monitoring. However, a desire remains for improved production techniques for enabling fabrication of fully wearable and flexible microfluidic devices or systems on textiles or other flexible substrates. Some development of certain flexible microfluidic devices such as pH sensors or biosensors have been proposed using paper-based flexible microfluidic devices technologies. In some such cases, paper is for forming fluidic microchannels, however, typical such paper-based fluidic channels are not sufficiently durable and typically cannot be used repeatedly, making them unsuitable for many wearable applications or for integration with clothing.
In view of the foregoing, there remains a need for new and improved fabrication processes and devices that enable production and implementation of flexible and wearable microfluidic devices and sensors, and in particular, flexible and wearable microfluidic devices and sensors which may be implemented on textile or other flexible substrates without hindering the flexibility of the textile. There additionally remains a need for improved microfluidic fabrication processes which address some of the limitations of existing techniques and devices, such as improved processes and devices which may desirably provide one or more of improved efficiency, increased speed, reduced cost and increased simplicity of microfluidic device production.